In the manufacturing of rotors, aluminum bars are extended, cut and installed into an iron core, which may consist of laminations of powder metal via slot openings. Aluminum end rings are machined from thick aluminum plate and positioned on each side of the iron core to mate with the extruded bars. Multiple passes of weld are required to attach the bars and end rings as well as to build up enough aluminum material to meet the end ring cross-sectional area requirement for the rotor without voids. The rough shaped welded end rings are then machined to the desired shape. This manufacturing process, particularly the welding, is very lengthy due to cooling time in between weld passes. In addition, machined end rings are very time consuming to manufacture and are expensive. Approximately 80-90% of the base material is scraped after machining. Post machining operations of the welded end rings are not desirable. It has been estimated that approximately 17% of additional aluminum is added during welding to allow for final machining which the material is lost as scrap.
With respect to the cast aluminum cage technique, the iron core is loaded into a casting die. A molten aluminum shot size is loaded into the die casting press. The bars and end rings are then cast. The cast rotor assembly is then cleaned and gates are removed. The iron core outer diameter is then machined to remove the aluminum flash created from the casting process. The manufacturing difficulties associated with this process includes high capital investment for casting equipment. Further casting porosity is generally a quality concern that is hard to control and identify in production. Additional iron core material is required on the outside diameter to allow for post machining of casting flash. Post machining operations, which are not desirable in general, are required to remove aluminum flash. If the process is subsequently out sourced to suppliers, finding good casting sources capable of casting the hybrid type rotor sizes is exceedingly difficult.
It is an object of the present invention to provide a manufacturing process utilizing extrusion capability for the shape of the iron rotor that is required. It is a further object of the present invention to provide a single weld pass to attach the bars and end rings to the iron core.